The freezing and thawing of large amounts of bulk liquids packed in flexible bags and/or rigid containers takes a long time due to limited cooling capacity of the freezing equipment, low overall heat transfer coefficient and the large size of the containers. This will affect the homogeneity of the products being frozen due to changes in product concentration throughout the container as it freezes.
Rapid or shock freezing is intended to alleviate these issues by reducing the freezing time and helping to maintain uniform concentrations, while quick thawing effectively converts the frozen product back to its liquid state so it can be readily used.
Current state-of-the-art fast freezing technologies utilize cabinet freezers and modified freeze dryers where packaged liquids are placed on or between cooled shelves, which
are cooled using mechanical and sometimes cryogenic cooling systems. The rate of freezing is determined by the overall thermal resistance of the systems which in this case quite high due to slow heat transfer through the packaging wall as the heat needs to pass through multiple protective layers designed to prevent damages as a result of contact with cold media as well as ineffective heat transfer on the inside of the package primarily due to natural convection.
The present invention provides a method and apparatus for addressing these shortcomings and improving the freezing of liquids.